In the prior art, there has been used a heat exchanger in which metal fins are joined with a metal tube or pipe by welding or the like, and the joined fins and metal tube or pipe are integrated with a header tank by caulking or the like. Recently, in order to reduce the impact on the global environment, there is a growing need for improvement of fuel efficiency owing to lightening of a vehicle, such as an automobile. Also in the fields of household appliances and OA, the reduction in size and weight is strongly desired. In response to those needs, there have been intensified tendencies to substitute materials or optimize shapes for the prior art heat exchanger. Specifically, there has been proposed an all-resin heat exchanger in which all components are resinified. The resinified components can realize the extension of the degree of freedom of the shape, and it is considered that if the heat exchange efficiency can be ensured, it is very advantageous in terms of reduction of weight and size of the entire apparatus.
As an example of a resin heat exchanger, Patent Document 1 discloses a technique that a plurality of resin tubes having a single refrigerant circulation hole are individually set in a mold so as to penetrate through a cavity, and the tubes set in the mold are injection-molded, whereby the resin tubes and a seat plate are connected to each other. Patent document 2 discloses a technique that a plurality of flat perforated tubes having a plurality of refrigerant circulation holes are each set in a mold in the same manner as for Patent Document 1, and a resin material is injected, whereby the tubes and a seat plate are integrally molded.
Patent Document 3 discloses a technique that grooved sheets formed of a resin are joined so as to face each other, whereby a tube having a refrigerant passage is formed, and, at the same time, tanks are formed at the both ends.
The resin heat exchanger disclosed in Patent Document 4 has components each formed of a resin material, and plates (headers of tubes) formed by double injection are provided at the both front ends of the tubes, and a header tank is joined with the plate.    [Patent Document 1] Japanese Patent No. 3488470    [Patent Document 2] Japanese Patent Application Laid-Open No.    [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-108644    [Patent Document 4] Japanese Patent Application Laid-Open No. 2002-225138